EP0325529A1 - Process and device for regulating dye supply - Google Patents

Abstract

The regulation of the dye bath is obtained, whilst following the depletion of dyestuffs in the bath by photocolorimetry, by varying in two successive steps firstly a first parameter and then a second parameter different from the first, in such a way that the depletion of dyestuffs in the bath as a function of time follows substantially a predetermined curve. For the dyeing of cellulose materials by reactive dyestuffs, in the first step the content of electrolytes will be increased and then in the second step the content of alkaline agent will be increased. For the dyeing of wool and polyamide with soluble dyestuffs from a spent recycling bath at approximately 70 DEG C, the pH value will be raised from neutrality to approximately 5, and then the temperature will be raised to 100 DEG C, if necessary. <IMAGE>

Description

The present invention relates to the regulation of a discontinuous operation for dyeing a material, in particular a textile material, during which the dye (s) present in the dye bath migrate onto the material and are fixed therein so sustainable. It concerns the regulation according to which the transfer of the dyes, that is to say the exhaustion of the bath in dyes, is monitored by photocolorimetry at determined time intervals and action is taken to ensure that the exhaustion in question follows a curve fixed in advance.

A regulation of this type is known and practiced, in which one acts on the temperature of the bath. The aim is to obtain a regular transfer of the dye (s) contained in the bath, essential for a homogeneous dye of good quality. Thus, a rate of depletion of the bath is determined in advance throughout the duration of the dyeing operation, or possibly different speeds of depletion of the bath during certain portions of the dyeing operation. And the temperature of the bath is varied, as a function of the values obtained, periodically, as to the actual depletion of the dye bath, so that the actual depletion curve is as close as possible to the pre-established curve.

This known method of regulation is implemented in a device sold under the brand TEINTOPROG. This device has three elements, namely the measurement chamber in which the bath circulates continuously, the optical unit consisting of a white light source associated with a set of four filters, photodiodes and converters and a processing system which analyzes the signals from the optical unit, processes them and controls the regulation by acting on the heating automation.

However, the known method is only operational for a limited number of types of dyeing, using soluble dyes, that is to say cationic or anionic dyes for wool, polyamide or acrylic. Its use is in particular not possible in the case of reactive dyes.

However, we have found, and this is what is the subject of the invention, a method of regulating a discontinuous dyeing operation, of the type of that known above, which provides significant diversification in possible applications. The method is of the known type according to which the exhaustion of the dye bath is followed by photocolorimetry at determined time intervals. In an original manner, one makes vary in two successive stages, first a first then a second parameter different from the first, so that the depletion of the dyes bath as a function of time substantially follows a predetermined curve.

Thus, we no longer act solely and throughout the duration of the dyeing on the sole temperature of the bath, but we act in a first step on a first parameter and in a second step on a second parameter, different from the first, one either of these parameters may be the temperature of the bath. It has in fact been observed that it is possible in a large number of applications, other than dyeing with soluble dyes for wool, acrylic or polyamides, to regulate the exhaustion of the bath throughout the dyeing operation. by successively varying two different parameters, said parameters being selected according to the application chosen.

In a first version of the invention, a dyeing bath for cellulosic materials containing at least one reactive dye is regulated, by increasing in a first step the content of electrolytes in the bath and by increasing in a second step the content of agents in the bath. alkaline.

As regards cotton, the electrolyte added to the bath during the first stage consists for example of sodium hydroxide, the alkaline agent added to the bath during the second stage consists for example of sodium hydroxide solution and the transition from the first stage to the second occurs, for example, when an additional supply of electrolyte no longer varies exhaustion.

In a second version of the invention, a dyeing bath for materials such as wool, polyamide, containing at least one soluble dye, is regulated. of a dyeing operation completed from the same batch and having a temperature of around 70 ° C and a pH close to neutral. In this second version, the pH is varied in a first step up to the known pH suitable for the material and the class of dyes used, for example 5, by progressive addition of an acid agent, then it is varied in a second. step the bath temperature to around 100 ° C.

Thus, thanks to the process of the invention when splitting the same batch, it is possible to recycle the used and hot dye baths, while being assured of having for all successive passes a homogeneous quality dye. This possibility of recycling represents an important energy saving, because until now the baths used were rejected or at best sent in heat exchangers, to recover part of the available energy. The latter solution was not always suitable, since this recovery involves the risk of fouling of the heat exchanger and therefore of reducing its performance. On the other hand, thanks to the invention, it is now possible to envisage recycling the dye baths, after use, up to five times successively or more.

• a. un capteur photocolorimétrique comprenant une chambre de mesure dans laquelle le bain de teinture circule, un bloc optique constitué au moins d'une source de lumière blanche placée d'un côté de la chambre et des moyens de traitement capables de mesurer à des intervalles de temps déterminés , à partir du flux lumineux transmis par le bain, la concentration du bain dans chacun des colorants,
• b. des moyens de comparaison, pour chaque colorant, de la vitesse d'épuisement constatée entre deux mesures successives par rapport à une vitesse présélectionnée,
• c. des premiers moyens d'action , agissant pendant la première phase du cycle de teinture , et commandés par les moyens de comparaison de telle sorte que la vitesse d'épuisement constatée soit proche de la ou des vitesse (s) d'épuisement présélectionnée pour cette première phase,
• d. et des seconds moyens d'action , agissant pendant la seconde phase de cycle de teinture, et commandés par les moyens de comparaison de telle sorte que la vitesse d'épuisement constatée soit proche de la ou des vitesse(s) d'épuisement présélectionnée(s), pour cette second phase.

It is another object of the invention to provide a device specially designed for the implementation of the above method. The device includes:

• at. a photocolorimetric sensor comprising a measurement chamber in which the dye bath circulates, an optical unit consisting at least of a white light source placed on one side of the chamber and processing means capable of measuring at time intervals determined, from the light flux transmitted by the bath, the concentration of the bath in each of the dyes,
• b. means for comparing, for each dye, the exhaustion speed observed between two successive measurements with respect to a preselected speed,
• vs. first means of action, acting during the first phase of the dyeing cycle, and controlled by the comparison means so that the speed of exhaustion observed is close to the speed (s) of preselected exhaustion for this first phase,
• d. and second means of action, acting during the second phase of the dyeing cycle, and controlled by the comparison means so that the speed of exhaustion observed is close to the speed (s) of preselected exhaustion ( s), for this second phase.

The first and / or second means of action may consist of containers fitted with a supply valve, the opening and closing of which are controlled by the comparison means, said containers containing given auxiliary dyeing agents. For example, the container corresponding to the first means of action contains an electrolyte and the container corresponding to the second means of action contains an alkaline solution. For example, the container corresponding to the first means of action contains an acid solution.

The first or second means of action may consist in the means for heating the dye bath provided with a switch actuated by the comparison means.

The invention will be better understood on reading the description which will now be made of two exemplary embodiments, illustrated by the appended drawing in which the single figure is a schematic sectional view of a regulation device, based on two parameters , equipping a dye autoclave.

The material to be dyed, not shown, is placed in the dye autoclave 1, on which a pipe 2 is mounted in diversion. The dye bath 3, circulating in the autoclave 1 during the dyeing operation, also circulates in continuous inside the pipe 2. The pipe 2 passes into the measurement chamber 4, which is connected by a double set 5 and 6 of optical fibers to an optical unit 7. The optical unit 7 comprises two parts 8 and 9 In the first part 8, a source 10 of white light and its associated optics 11 illuminate the input 12 of the first set 5 of optical fibers. In the second part 9, the output 13 of the second set 6 of optical fibers is directed to four filters, associated with photodiodes and converters, transforming the light flux transmitted through the filters into electrical signals. The four filters are chosen so that their transmission spectra have maximum peaks which together cover the range of wavelengths between 400 and 700 nanometers. In the measurement chamber 4, the pipe 2 comprises the outlet 14 of the first set 5 of optical fibers and the inlet 15 of the second set 6 of optical fibers. The outlet 14 and the inlet 15 are positioned opposite one another in the pipe 2.

The converters are connected to an assembly 16 for processing electrical signals, the operation of which will be explained later, which controls the use of the solenoid valve 17 fitted to the container 18 on the one hand and the automatic control system on the other hand. heating 19 of the dye bath 3. The container 18, containing at least one dyeing agent, opens into the autoclave 1.

The implementation of the method of the invention and the operation of the aforementioned device will be described in a first following example of bath dye in fluff, using a recycling bath.

The spent bath, after a first wool dyeing operation, is substantially free of dyes; it is at the end of the cycle temperature, of the order of 90 ° C to 100 ° C. The quantity of spent bath is less than that necessary for a new pass, taking into account the quantity of bath which was removed by the material taken out of the autoclave in the previous operation. When supplemented with cold water, the temperature of the spent bath is around 75 ° C. Its pH is brought to 7.4, optionally adding the necessary reagents. The photocolorimetric sensor performs a first measurement of the spent bath and then a second after adding the dyes.

The flock of yarn to be dyed is placed in the autoclave and the dyeing operation can begin. In the autoclave, the dye bath 3 passes through the material to be dyed and circulates in line 2.

The light source 10 associated with its optics 11 sends a flux to the input 12 of the first set 5 of optical fibers light which is directed into the measurement chamber 4. In the chamber 4, this flux coming from the exit 14 of the first set 5 of optical fibers crosses the dye bath 3. The incident light flux undergoes an absorption which is a function of the concentration by coloring bath 3, for a given wavelength of light. The flow, after passing through the bath 3, is taken up by the second set 6 of optical fibers and is separated into four distinct channels where it passes through each of the four filters. The purpose of passing over the filters is to reveal the specific luminous flux of each dye contained in the bath as a function of its wavelength. The photodiodes, the converters and the processing unit 16 convert the light intensities into standardized currents (from 4 to 20 mA).

Prior to the dyeing operation, a set value (s) corresponding to the desired depletion rate (s), for example 1.5% per minute, was introduced into the treatment unit. This value is the difference in the concentrations measured between two measurements made by the sensor compared to the time interval between said two measurements.

During a first step, the processing assembly 16 acts on the solenoid valve 17 controlling the introduction into the autoclave 1 of the acetic acid solution contained in the container 18. This introduction is controlled so that the speed d he actual exhaustion is close to the set speed (s) used for this first step. Thus, the processing assembly 16 will command the opening of the solenoid valve 17 at each measurement where a negative difference will be noted between the measured value and the setpoint value (measured exhaustion speed lower than the exhaustion value adopted as the setpoint Conversely, in the event of a positive deviation exceeding a given maximum, the processing assembly 16 will not control the opening of the solenoid valve 17.

This first step, in the case of dyeing wool fluff using soluble dyes, lasts until the dye bath 3 has reached the predetermined pH threshold, depending on the material and the class of dyes, for example 5. This predetermined pH is that recommended by the suppliers of dyes and known to all dyers.

In the second step, the processing assembly 16 acts on the automatic device 19 for heating the dye bath 3, increasing or stopping the heating so that the actual speed of depletion is close to the speed (s) (s) setpoint retained for this second step.

This second step lasts until the temperature reaches 100 ° C or when the dye bath 3 is exhausted to 90% for example.

Then the temperature is maintained during the end of dyeing stage.

In another example of cotton dyeing using reactive dyes, the processing assembly 16 is connected not to the heating automation 19 but to a second solenoid valve / container assembly similar to the solenoid valve 17 and to the container 18 In this case, the first container 17 contains an electrolyte, for example sodium hydroxide and the second container an alkaline solution, for example sodium hydroxide solution.

The operation of the device is identical to that described in the first example. The dye bath remains at constant temperature, for example around 40 ° C if the reactive dyes used are "cold" reactants, 80 ° C if the reactive dyes used are "hot" reactants. In the first step, the electrolyte is added so that the measured exhaustion speed is close to the set speed selected for this first step, which lasts until an additional supply of electrolyte no longer makes vary exhaustion. This transition from the first to the second step is controlled when, for example during four or five successive measurements, the colorimetric sensor no longer notices any change in the exhaustion of the dye bath. It is also possible to fix, for a given dye, a predetermined quantity of electrolyte and to go from the first to the second stage when this predetermined quantity has been added to the bath. To choose the predetermined quantity, we will use the tables, supplied by dyestuff suppliers and made available to all dyers, which indicate the desired electrolyte concentration in the dye bath.

In the second step, the alkaline solution is added so that the measured exhaustion speed is close to the set speed selected for this second step, which lasts until all of the alkaline agent is used, or ideally that an additional intake no longer varies exhaustion.

In a specific case, a cotton containing 0.5% of a reactive dye CI (Color Index) Reactive yellow 27 was used for a cotton which has previously undergone the necessary preparation treatments. This percentage is calculated on the mass of material to be dye. The bath, maintained at 40 ° C., circulates through the material for 5 to 10 minutes for good homogenization, then the sodium sulfate is added so that the exhaustion in dye follows a slope of 1.5% / min. For the quantity of dye and the bath ratio, the quantity of sodium sulphate retained is 40 g / l. The end of the first stage occurs when the amount of sodium sulfate, corresponding to 40 g / l, has been added to the bath. The alkaline agent is a sodium hydroxide solution at 36 ° Bé, at a rate of 2 ml / l. the exhaustion curve for this second step is the same, namely 1.5% / min. The end of the second stage occurs when the quantity of lye provided has been added or when no depletion is observed after 5 successive additions of lye. The complete fixing of the dye and the usual finishing treatments (rinsing, soaping) require an additional time of approximately 30 minutes.

The invention is not limited to the examples which have just been described. It is up to the person skilled in the art, within the framework of the process of the invention, to choose the two parameters which will best allow the speed of exhaustion of the dye bath to be varied as regularly as possible, and this as a function of the dyestuffs and dyeing conditions.

Claims (9)

1. Method for regulating a dye bath of the type according to which the exhaustion of the bath is followed by coloring by photocolorimetry, characterized in that it is varied in two successive stages, first a first then a second parameter different from the first, so that the depletion of the dye bath as a function of time substantially follows a predetermined curve. 2. Method according to claim 1 characterized in that, in the case of a dyeing bath of a cellulosic material containing at least one reactive dye, in the first step the content of electrolytes is increased in the bath and in the second step the content of alkaline agents in the bath is increased. 3. Method according to claim 2 characterized in that the electrolyte and the alkaline agent added to the bath are respectively sodium sulphate and a sodium hydroxide solution, and in that the transition from the first to the second stage occurs when an additional supply of sodium sulfate no longer varies the exhaustion of the bath. 4. Method according to claim 1 characterized in that, being a dye bath containing at least one soluble dye, having a temperature of about 70 ° C and a pH close to neutral, in the first step we varies the pH to the pH suitable for the class of dyes and in the second step the temperature of the bath is varied up to approximately 100 ° C. 5. Method according to claim 4 characterized in that the variation of the pH is obtained by addition of acid, in particular acetic acid, and in that the transition from the first stage to the second occurs when the pH is equal to 5. 6. Application of the method according to one of claims 4 and 5 to the regulation of hot recycling baths. 7. Device for implementing the method of claim 1 characterized in that it comprises: at. a photocolorimetric sensor comprising a measurement chamber (4) in which the dye bath (3) circulates, an optical unit consisting of at least one white light source (10) placed on one side of the chamber and processing means (9) capable of measuring at determined time intervals, from the light flux transmitted by the bath, the variation in concentration of the bath in each of the dyes, b. comparison means (16), for each dye, of the exhaustion speed observed between two successive measurements with respect to a preselected speed, vs. first means of action (17, 18), acting during the first phase of the dyeing cycle, and controlled by the comparison means (16) so that the speed of exhaustion observed is close to the speed (s) s) pre-selected exhaustion for this first phase, d. and second action means (19), acting during the second phase of the dyeing cycle, and controlled by the comparison means (16) so that the speed of exhaustion observed is close to the speed (s) ) pre-selected exhaustion (s), for this second phase. 8. Device according to claim 7 characterized in that the first and / or second means of action consist of containers (18) provided with valve (17) supply whose opening and closing are controlled by the means of comparison (16), said containers containing given auxiliary dyeing agents. 9. Device according to claim 7 characterized in that the first or second means of action consist of the means (19) for heating the dye bath provided with a switch actuated by the comparison means.

Images